1. Field of the Invention
The present invention relates generally to an apparatus and method for transmitting control information in a wireless communication system, and in particular, to an apparatus and method for transmitting fast feedback information in a Broadband Wireless Access (BWA) communication system.
2. Description of the Related Art
A mobile communication system is a typical wireless communication system. The mobile communication system is gradually evolving into a system capable of providing wireless packet data service based on voice service. The 3rd Generation (3G) mobile communication system that can provide wireless packet data service is developing into a system capable of providing various multimedia services at a high rate. The 3G mobile communication system identifies users using a Code Division Multiple Access (CDMA) scheme. The CDMA scheme can transmit data by allocating different orthogonal codes or transmission data to users.
However, the 3G system cannot provide data at a higher rate with higher quality due to a lack of codes. That is, the 3G system is limited in data rate due to a restriction of available codes. In order to address this problem, mobile communication system developers are taking into consideration a 4th Generation (4G) BWA communication system, referred to as the next generation communication system. The 4G system can classify users or user data using an Orthogonal Frequency Division Multiple Access (OFDMA) scheme before transmission. The 4G system can increase data rate up to about 100 Mbps. Therefore, compared with the 3G system, the 4G system can provide services with various Qualities-of-Service (QoS).
Research on the 4G system now focuses on the BWA communication system such as a wireless Local Area Network (LAN) system and a wireless Metropolitan Area Network (MAN) system. The BWA communication system is evolving into a system capable of guaranteeing QoS, providing mobility which is the characteristic of a wireless communication system. An Institute of Electrical and Electronics Engineers (IEEE) 802.16a communication system and an IEEE 802.16e communication system are typical BWA communication systems. In addition, various other systems are being developed using the OFDMA scheme.
The BWA communication system is developing into a system that basically uses the OFDMA scheme and can guarantee mobility. For data transmission, the BWA communication system transmits Orthogonal Frequency Division Multiplexing (OFDM) symbols basically using a Time Division Duplexing (TDD) scheme. In transmitting OFDM symbols, the BWA communication system divides the OFDM symbols into a downlink and an uplink in a period of a particular time domain because it uses the TDD scheme. Each of the downlink and the uplink transmits OFDM symbols in particular slots. Such a BWA communication system can distinguish the OFDM symbols as physical channels having a separate particular purpose in the uplink and the downlink.
The OFDMA-based communication system has physical channels for fast feedback in the uplink. Information included in the physical channels for fast feedback includes perfect signal-to-noise ratio (SNR) information, per-band differential SNR information, fast Multi-Input Multi-Output (MIMO) feedback information, mode selection feedback information, MIMO feedback information, etc. The perfect SNR information refers to an SNR for a full band. Such fast feedback information for the uplink requires a guarantee of high reliability because it is very important for application of a communication system although it is large in quantity.
In transmitting the fast feedback information in the uplink, the conventional technology transmits 6-bit information using one uplink subchannel. However, transmitting only the fixed 6-bit information using one uplink subchannel causes a lack of application flexibility for a system requiring various feedback information, for example, for a MIMO system that has multiple antennas and requires feedback information for each individual antenna or stream. This is because the multi-antenna transmission system requires information on various wireless channels in order to acquire optimal performance while using a plurality of transmission antennas.
Therefore, the multi-antenna transmission system requires diverse feedback information according to a multi-antenna transmission algorithm. However, presently there is no proposed scheme for a method capable of providing the diverse information.